Cosmetic formulations containing lipids are well known. Lipids can function to produce the desired consistency and viscosity in a formulation and, more importantly, to help replenish lipids in the skin.
Since most lipids commonly used in cosmetic formulations contain unsaturated chains, such formulations are susceptible to oxidation. Oxidative damage can lead to loss of alkyl chains, which results in loss of fluidity and lipophilic properties, e.g., the ability to replenish lipids in the skin and thus impart suppleness and youthful appearance. Oxidation can also lead to discoloration and development of unpleasant odors. Oxidative damage can be attributed, in particular, to radiation-induced free radical reactions.
In addition to minimizing oxidation, it is desirable to enhance the moisturizing properties of cosmetic formulations; i.e., the amount of moisture that can be retained by the skin when the formulation is applied. Increased moisturizing effectiveness is also important in topical therapeutic lipid formulations, such as are used in treating dry eyes.
Finally, it is desirable that the lipids themselves are stable; e.g., that they not be readily oxidized or hydrolyzed.